1. Field of the Invention
The present invention relates to reinforced construction in general and, more particularly, woven reinforced construction which provides a lightweight, dimensionally stabilized framework.
2. Description of the Prior Art
A novelty search in the field of lightweight construction designed particularly for laser applications disclosed no pertinent prior art that fully solved the problems inherent in many of the laser operations.
About half of all laser applications involve the use of some sort of "interference" which is a means of causing a laser beam to cancel itself out and taking note of how this happens. Interference technology, because distances as small as fractions of the wavelength of light are involved, requires the most exacting dimensional stability in all supporting equipment. Mirrors, lenses and other components must be located on an "optical bench" for example, as precisely as possible in relation to each other.
Thermal effects are a problem. Temperature changes can cause interference fringes which should be stationary, to zip past in a steady stream. This problem is so sensitive that if an operator should happen to place his hand on a laser support the system can produce enough heat to cause the same effect. Thermal instability in the laser support system is critical.
Another major problem in interferometry is vibration. Even seismic vibrations coupled from the earth must be isolated. A common strategy is to supply sufficient mass in the support so that its inertia will cancel out the effects of vibration. However, the use of a multi-ton granite block for an optical bench usually contends with the problem of the block supporting its own weight. Also, some large masses tend to have natural resonances so that certain acoustic frequencies are amplified, not reduced.
In view of the above problems it is obvious that laser support equipment and the like require a dimensionally stable, zero expansion structure capable of distributing internal stresses uniformly throughout the system.
One general approach to the aforementioned problems is a three dimensional structure which exploit graphite and other composites involving some sort of "honeycomb", which is hexagonal piping that resemble that found in beehives. The honeycomb principle is used in everything from space telescope to the ailerons on airliners. The honeycomb structure is far too complex to weave from carbon fibers and normally requires hand assembly of any material. It is an expensive operation.
Aside from the honeycomb system there are several prospects that may well produce a lightweight structure of carbon fibers. One is known as the "socket method" which proposes to use carbon rods or lengths of stiff fiber struts. One end of the struts is inserted in a socket member having a plurality of cup-like projections extending angularly therefrom to receive the inner ends of the struts. The struts fan outwardly and have the outer end enclosed in caps.
Experience has shown that in the socket method a completed structure will develop cumulative tolerances which produce gaps between the struts within the socket member. In this case the thermal expansion of the socket comes into play. This could be disastrous because if an assembly of sockets and struts have variable gaps, which tend to happen, the dimensional stability of a structure is lost.
In another case whereby a woven structure may be achieved is by the so-called "junction method". Here the bundle of carbon fibers fork outwardly in angular directions from a fixed junction of fibers. The problem with the fixed junction method is that the strut of fibers are ridgedly held at the junction and expansion in the radial direction produces a vector in the axial direction of adjoining struts. This would obviously produce an accumulative positive expansion greater than the negative expansion (shrinkage) in the struts and the desirable property of zero expansion throughout the structure is then impossible to obtain.
Further search disclosed several patents relating to carbon formed structures. Of such patents of interest there were two having to do with methods of forming carbon composites. These are U.S. Pat. Nos. 4,193,828, and 4,252,588. Both produce products or structures which do not read on the structural design and results achieved by the present invention.
Four patents, namely, U.S. Pat. Nos. 3,599,107, 3,546,049, 3,763,442, and 4,219,597 show composites which are used or may be used in structural concepts.
U.S. Pat. No. 3,546,049 shows the joining of at least four beams oriented on a non-Cartesian axes with rigidity or foldability as required, each beam having elongated component elements, the axes of the beams joined preferably meeting at a common point, the elements crossing but not intersecting in a region of beam intersection, the beams being interleaved in fixed and regular patterns.
U.S. Pat. No. 3,763,442 shows a device for cooling an ion laser plasma tube based on the utilization of a thermal conductor adapted to become fused to an ion laser plasma tube in such a manner as to efficiently transfer the heat generated to a surrounding cooling medium while mechanically adjusting to differential thermal expansion and contraction of the plasma tube.
U.S. Pat. No. 3,599,107 shows a gas laser including a quartz insulator tube enclosing a stack of graphite discs having a central aperture forming a laser discharge path wherein the individual discs are spatially separated and electrically insulated from one another by quartz rods inserted into spacer holes disposed about the central apertures, the depth of the spacer holes in the discs intermediate the end discs being constructed and arranged in a manner to compensate for thermally induced variations in the length of the stack.
U.S. Pat. No. 4,219,597 shows a structure comprising more than four bundles each constituted by a plurality of regularly spaced, parallel, rectiliner elements, the directions of at least five of each bundles being oriented parallel to at least five of the ten directions defined by the lines connecting the non-contiguous vertexes of a parallelepiped in twos and the bundles taken in threes not constituting a system in which each bundle is perpendicular to the other two.
From the information cited above concerning materials, construction techniques and potential results none of the references will produce a regular, three dimensional geometric matrix having the property of zero expansion and uniform distribution of stresses throughout the three planes of the structure. The present invention provides such a structure which solves the problems mentioned for laser application, and many application in other fields.